I'm making a bike light out of some of those ultra bright LEDs I got for my n46p (I had 100 of them lol) but the resistors that came with them only allow full brightness at 12v. I'm going to have a 3.6v battery, so how much resstance should I use?
Since the voltage will be 10/33 as much as normal, does that mean it will be the same brightness if my resistors have 10/33 as much resistance as the original one?
If I have 20 LEDs, does that mean I can use just one resistor but with 1/20 as much resistance and connect all the LEDs to it?
How much should I lower resistance of I lower LED voltage?
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How much should I lower resistance of I lower LED voltage?
Last edited by daguuy on Sun Jun 17, 2007 10:09 pm, edited 1 time in total.
So what do you mean by full brightness at 12v? That doesn't make much sense, the brightness is regulated by the current....so you should set the current to whatever the best value is by selecting the right resistor based on the supply voltage and forward voltage drop of your LEDs. I hope the forward drop isnt 12v...that would be some pretty crazy LEDs
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lol, did you buy your LEDs on eBay from hong kong?
Cause I did, and they (similarly ?) are ultrabright whites that came with "12v" resistors.
So all that means is that someone put the numbers into an LED resistor calculator with the power supply set at 12v.
I actually converted one of my flashlights to use lithium batteries and LEDs just recently. I took pics but I never got around to writing it up... It has a cool custom protection circuit.
anyways, the forward voltage of a bright white led is somewhere around 3.5v. this is very close to the working voltage of the battery, I used 10 ohm resistors, to be safe when the battery is fully charged (4.2v) (and cause you shouldn't put LEDs in parallel with no resistor..) my point is that you dont need much of a resistor. put the numbers into a resistor calculator and it will give you something less than 10 ohms.
btw the flashlight is surprisingly bright with only 3leds. like brighter than a normal flashlight.
Cause I did, and they (similarly ?) are ultrabright whites that came with "12v" resistors.
So all that means is that someone put the numbers into an LED resistor calculator with the power supply set at 12v.
I actually converted one of my flashlights to use lithium batteries and LEDs just recently. I took pics but I never got around to writing it up... It has a cool custom protection circuit.
anyways, the forward voltage of a bright white led is somewhere around 3.5v. this is very close to the working voltage of the battery, I used 10 ohm resistors, to be safe when the battery is fully charged (4.2v) (and cause you shouldn't put LEDs in parallel with no resistor..) my point is that you dont need much of a resistor. put the numbers into a resistor calculator and it will give you something less than 10 ohms.
btw the flashlight is surprisingly bright with only 3leds. like brighter than a normal flashlight.
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